Add 1 tablespoon olive oil into a large nonstick skillet over medium-high heat. Once oil is hot, add onion and saute until browned, about 8 minutes.

Season the onions with red pepper flakes, salt, pepper, and chopped parsley. Remove onions from the skillet to a bowl and reserve.

Add the remaining tablespoon oil to the hot skillet. Once hot, add the burgers and cook for 3 to 4 minutes until very browned on one side. Flip and continue cooking the other side for another 3 minutes. Remove from pan.